I'm building some new antenna cables from a super-flex equivalent to LMR-240 coax cable. This is exactly the same size as RG-59 cable but this particular cable has a stranded core and a polyurethane jacket.

Prior to installing the crimp BNC connectors, I slide a Pomona 5515-0 rubber boot onto the cable. I then slide the boot over top of the connector's ferrule after its been crimped.

These Pomona 5515 rubber boots are intended for use on RG-58 cable. They are a tight fit on this cable but, by lubing them up with Hellerene lubricant (intended for Hellermann neoprene insulating sleeves), they usually go on the cable with no problem.

Most cable, that is. No problem with real LMR-240 cable and the clone cable that I normally use (DBRF-240, FLL-240), all of which has a solid core and polyethylene jacket.

But this super-flex cable is just too, well, flexible. Its not rigid enough for me to twist and push the rubber boot on, no matter how much lube I use.

I've been faking it by using a beefy pair of long-nose pliers to expand the boot just before I slide it onto the cable. But the pliers don't go into the boot far enough to be completely effective. I do both ends of the boot but the middle portion is still too small to slide easily onto this super-flex cable.

What I'm looking for is some method of easily expanding these boots long enough to get them onto the cable. They can then retract to their normal diameter and not cause me any grief.

My first thought was to grab two pieces of 0.20" drill-rod and grind an flat taper over a 3" length on each. Insert one piece in each end of the boot, then use a press to slide the tapers past each other and thus expand the boot.

Couple of problems with this approach:

1) Its probably gonna be hard to pull the drill rods back out of the boot. I can see myself clamping one end of one of the rods in a bench vise, then levering the boot off of the rod. But: it will probably work.

2) Its not portable for field work. The rods themselves are certainly tiny and easy to toss into a tool-kit, but I can't see myself packing my hydraulic press to job-sites. Not the bench vise, either..

What I'd love to find is something that uses a screw to pull a wedge through the boot. It would be child's play to chuck the screw into a battery drill.

But I can't quite envision the whole thing. So: PIClist to the rescue, I hope.

On 06/01/2012 11:30 PM, Dwayne Reid wrote:
> What I'm looking for is some method of easily expanding these boots
> long enough to get them onto the cable. They can then retract to
> their normal diameter and not cause me any grief.

At 12:30 AM 6/2/2012, you wrote:
>either.
>
>What I'd love to find is something that uses a screw to pull a wedge
>through the boot. It would be child's play to chuck the screw into a
>battery drill.
>
>But I can't quite envision the whole thing. So: PIClist to the
>rescue, I hope.
>
>Anyone have any ideas?

On 6/2/2012 12:30 AM, Dwayne Reid wrote:
> But this super-flex cable is just too, well, flexible. Its not rigid
> enough for me to twist and push the rubber boot on, no matter how
> much lube I use.
>

Have you considered using heat shrink tubing in place of the rubber boot ?
There a couple manufacturers that make waterproof heat shrink tubing, I use it for electronics that go inside aquariuns.
It has an adhesive glue, similar to hot melt glue sticks that seals the connection tight.http://www.qualitydist.net/piwaheshbl.html

At 10:58 AM 6/2/2012, you wrote:
>On 06/01/2012 11:30 PM, Dwayne Reid wrote:
> > What I'm looking for is some method of easily expanding these boots
> > long enough to get them onto the cable. They can then retract to
> > their normal diameter and not cause me any grief.
>
> Would something like this work? If not, maybe it'll give some ideas?
>
>http://www.aircraftspruce.com/catalog/topages/stretcher.php
>
>Tad

The local Home Stores sell water tight heat shrink kits to seal up the 240 VAC connections on submersible water pumps. It seems to work.

On 6/2/2012 12:11 PM, Mark Hanchey wrote:
> On 6/2/2012 12:30 AM, Dwayne Reid wrote:
>> But this super-flex cable is just too, well, flexible. Its not rigid
>> enough for me to twist and push the rubber boot on, no matter how
>> much lube I use.
>>
> Have you considered using heat shrink tubing in place of the rubber boot ?
> There a couple manufacturers that make waterproof heat shrink tubing, I
> use it for electronics that go inside aquariuns.
> It has an adhesive glue, similar to hot melt glue sticks that seals the
> connection tight.
> http://www.qualitydist.net/piwaheshbl.html
>
> Any chance you could give us some pics of what the boot looks like ?
>
> Mark
>

-- John Ferrell W8CCW
“During times of universal deceit,
Telling the TRUTH becomes a revolutionary act”
George Orwell

Good thought but it won't work with this particular cable - it remains flexible down to under -55C. Its probably flexible at temperatures much colder than -55C but that's as cold as the data sheet says. Its that darned polyurethane jacket <grin>.

I have lots of different Hellermann (and others) sleeve expanding tools for Hellermann sleeves but they are both too short and not strong enough. I've been using these sleeves for a several decades now and keep collecting the older 3-prong cast Hellermann expanding tools as I come across them. I much prefer the old version of the tool compared to the current version being sold today.

For what its worth, I purchase black Hellermann PH20x20 sleeves 10,000 at a time. Those are 20mm long with an inside diameter of 2.0mm. Can you tell that I like using Hellermann sleeves <grin>?

Someone had suggested using adhesive-lined heat-shrink tubing. I used to do that but there is still too much flex right at the crimp ferrule. This leads to shield failure right at the connector.

The Pomona boots are so stiff at the connector that there is absolutely no flex at the ferrule. They then taper sufficiently thin that the cable flexes in the boot rather than where the cable exits the boot. The result is that the cables last for many years instead of many months. The usual failure is mechanical - the cable gets crushed or otherwise wrecked somewhere in the middle of the cable rather than failing at a connector.

Plus: the Pomona boots just look better.

These cables are used by TV broadcast mobile crews and professional football teams for RF intercoms and wireless mics. They are setup for a single event (mostly sports), then taken down and shipped to the next venue.

Most of the cables I build (many hundreds) are made with the stiffer LMR-240 type cable. There is simply no problem getting the boots on that cable - a few drops of Hellerine lube and they twist and slide right on. But I use the super-flex cable for the coaches comms used by professional football teams because the people setting up the gear are not technically-trained and they have real difficulties in working with the stiff cable that I prefer to use. Thus the use of super-flex cable.

> I'm building some new antenna cables from a super-flex equivalent to
> LMR-240 coax cable. This is exactly the same size as RG-59 cable but
> this particular cable has a stranded core and a polyurethane jacket.
>
> Prior to installing the crimp BNC connectors, I slide a Pomona 5515-0
> rubber boot onto the cable. I then slide the boot over top of the
> connector's ferrule after its been crimped.
>
> These Pomona 5515 rubber boots are intended for use on RG-58
> cable. They are a tight fit on this cable but, by lubing them up
> with Hellerene lubricant
>
> But this super-flex cable is just too, well, flexible.

How about the following procedure: select a heat shrink tubing that
is just slightly larger diameter than coax cable, cut a 6"-8" long
piece, stick 1/2" to 1" (1-3 cm for you Canadians :-) ) of coax cable
into the end of the heat shink tubing, shrink entire length of heat
shrink tubing down so it grabs coax cable & makes a several inch long
smaller diameter guide, slide lubed boot over guide portion, then pull
small diameter guide portion of heat shrink tubing with pliers to force
feed boot onto & over coax cable. Since you're pulling the coax cable,
its super-flex nature shouldn't be a problem.

Once boot is a couple of inches onto coax cable, use a knife to
carefull slice heat shrink tubing off of end of coax cable. It's
not a method that I'd use in a production situation, but you likely
have heat shrink tubing on hand and I think it's worth a try.

> How about the following procedure: select a heat shrink tubing that
> is just slightly larger diameter than coax cable, cut a 6"-8" long
> piece, stick 1/2" to 1" (1-3 cm for you Canadians :-) ) of coax cable
> into the end of the heat shink tubing, shrink entire length of heat
> shrink tubing down so it grabs coax cable & makes a several inch long
> smaller diameter guide, slide lubed boot over guide portion, then pull
> small diameter guide portion of heat shrink tubing with pliers to force
> feed boot onto & over coax cable. Since you're pulling the coax cable,
> its super-flex nature shouldn't be a problem.
>
> Once boot is a couple of inches onto coax cable, use a knife to
> carefull slice heat shrink tubing off of end of coax cable. It's
> not a method that I'd use in a production situation, but you likely
> have heat shrink tubing on hand and I think it's worth a try.

I was thinking something similar. Instead of using heat shrink tubing to reinforce the coax cable, use a thin walled metal tube that fits over the coax cable. Initially put a snug fitting metal rod inside the metal tube. Load the boot onto the tube. replace rod with coax cable. Slide boot from tube to cable.

>How about the following procedure: select a heat shrink tubing that
>is just slightly larger diameter than coax cable, cut a 6"-8" long
>piece, stick 1/2" to 1" (1-3 cm for you Canadians :-) ) of coax cable
>into the end of the heat shink tubing, shrink entire length of heat
>shrink tubing down so it grabs coax cable & makes a several inch long
>smaller diameter guide, slide lubed boot over guide portion, then pull
>small diameter guide portion of heat shrink tubing with pliers to force
>feed boot onto & over coax cable. Since you're pulling the coax cable,
>its super-flex nature shouldn't be a problem.

At 06:14 AM 6/3/2012, smplx wrote:

>I was thinking something similar. Instead of using heat shrink tubing to
>reinforce the coax cable, use a thin walled metal tube that fits over the
>coax cable. Initially put a snug fitting metal rod inside the metal tube.
>Load the boot onto the tube. replace rod with coax cable. Slide boot from
>tube to cable.

Thanks to both Lee and Sergio.

Both of your suggestions made me think of something that works easily and quickly.

I took 3.5" thin-wall brass tubing that just fits over the coax and another 3.5" piece that just fits (easily) inside the rubber boot. I cleaned one end of the larger piece both inside and out as well as the outside of one end of the thinner piece. I stuck the smaller piece into my lathe and used a smooth taper to expand the end so that it just fits inside the larger tube. I fluxed it well with Kester AZ2331 water-soluble flux and filled the outside of the taper with solder. Added more flux, then slide the small tube inside the larger. Also added some flux to the inside of the larger tube where the small tube exited.

I then chucked the larger piece into the lathe and used a piece of drill-rod in the tailstock that just fit inside the small tube. This kept everything concentric.

Fired up the lathe and used a smoothing tool to taper the larger tube down to the diameter of the small tube. Added more flux at the seam, then heated both tubes, also at the seam. Waited for the solder on the small tube to melt (inside the larger tube), then pulled the small tube as far out from the larger tube as possible - so that the outside taper on the small tube was up against the inside taper on the larger tube. Then added solder to outside of the seam.

The end result is a tube that fits over the coax, with a smooth taper down to a smaller tube that the boot fits over nicely. Lubed both the boot and the tubing, then slide the boot onto the small tube. Pushed the boot all the way onto the large diameter tubing, using my vise with the jaws set so as to allow the small tube to slide freely between. Then slipped the large tube over the coax and used the vise jaws to push the boot off of the large tube onto the coax. I had to pull on the small tube while pushing on the coax help the boot to move off the large tube onto the coax - the coax just wanted to fold and curl. But it was quick and painless.

The brass tubing is the standard stuff that you get at hobby shops - packaged by K&S. These are available in 1/32" increments and they just fit inside each other. That makes the wall thickness somewhat less than 1/64". I keep on hand several feet of each size from 1/16" all the way to 1/2" - its simply amazing how useful this stuff is. It forms beautifully on the lathe (tapers, etc) and solders easily.

I'm not sure how long it might have taken me to think of this solution - or even if I would have thought of this without your suggestions. And it was easy - it took longer to write up this email than it took to actually make the thing.

Will do on Wednesday or so - I'm away from the shop all day tomorrow. Tek has a couple of seminars only a few blocks away from me, so I'll go drool over their latest and greatest and listen to all the reasons why I really need new, expensive tools.

I *should* have taken pictures while I was making this thing - my new camera was only a few feet away from me all the while. I'm just not yet used to having a decent camera handy.

At 05:42 AM 6/3/2012, Lee Jones wrote:
>
>> How about the following procedure: select a heat shrink tubing that
>> is just slightly larger diameter than coax cable [...]

Dwayne wrote:

> Thanks to both Lee and Sergio.

You're welcome (from Lee).

> I took 3.5" thin-wall brass tubing that just fits over the coax
> and another 3.5" piece that just fits (easily) inside the rubber
> boot.
>
> Fired up the lathe and used a smoothing tool to taper the larger
> tube down to the diameter of the small tube [and soldered]

Well, I didn't _know_ that you had a lathe! :-)

> The brass tubing is the standard stuff that you get at hobby shops -
> packaged by K&S. These are available in 1/32" increments and they
> just fit inside each other. That makes the wall thickness somewhat
> less than 1/64". I keep on hand several feet of each size from 1/16"
> all the way to 1/2" - its simply amazing how useful this stuff is.
> It forms beautifully on the lathe (tapers, etc) and solders easily.

It truly is great stuff. I also keep a full range of nested sizes
from smallest to largest. You can easily make a splice for different
size vacuum hoses, a vacuum hose T fitting, bolt spacers, etc, etc.

At 06:20 AM 6/5/2012, Lee Jones wrote:
> >
> > Fired up the lathe and used a smoothing tool to taper the larger
> > tube down to the diameter of the small tube [and soldered]
>
>Well, I didn't _know_ that you had a lathe! :-)

If I hadn't had a lathe, I could have (and have done in the past) done this on my drill press. In a real pinch, could have done it in a hand-held power drill but that would have taken an extra person to hold the drill and keep its trigger pressed.

Where there is a will, there is (often) a way <grin>.

I met up with a buddy of mine today - he's also a PIClist member. He was sort of laughing at me, saying that the solution that we came up was obvious. Of course its obvious, after the fact. But I have these Hellermann tools that I use so often and was thinking of a bigger / longer / stronger version of the tool and it completely blinded me to a better solution. But: PIClist to the rescue!